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A FB at LHC

This presentation discusses the feasibility and significance of measuring AFB (forward-backward asymmetry) at the Large Hadron Collider (LHC). Led by Ronan McNulty, alongside researchers from the University of Liverpool and University College Dublin, the study highlights the current precision issues in sin²θW measurements and the impact of mass on AFB away from the Z pole. It emphasizes the potential for improved measurement sensitivity and addresses uncertainties related to theoretical predictions and parton distribution functions (PDFs), concluding that efforts to measure AFB at LHC are indeed worthwhile.

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A FB at LHC

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  1. AFB at LHC Myfanwy Liles (University of Liverpool) Ronan McNulty (University College Dublin) Tara Shears (University of Liverpool) LHCEWWG 5.04.2011 Ronan McNulty, LHCEWWG, 5.04.2011

  2. Outline • Is it worth trying to measure AFB at LHC? • Rather simple and unsophisticated study • Horace • Pythia • Motivate discussion and ideas Ronan McNulty, LHCEWWG, 5.04.2011

  3. Current precision on sin2qW Unsatisfactory that two most precise measurements are >3s apart, and that W.A. is marginally consistent with either. Would like to make measurement with precision of ~0.0001. Ronan McNulty, LHCEWWG, 5.04.2011

  4. HORACE: O()+-ind. 7TeV. All rapidities. AFB away from Z pole • Strong dependence with mass due to -Z interference. (To first order, zero on pole). “Asymmetry greater further from pole” Ronan McNulty, LHCEWWG, 5.04.2011

  5. AFB away from Z pole • On pole, due to different RH, LH Z coupling… • Small positive value HORACE: O()+-ind. 7TeV. All rapidities. Ronan McNulty, LHCEWWG, 5.04.2011

  6. AFB on Z pole AFB in muon channel at LHC is about 5 times larger than at LEP. But sensitivity coming more from Al rather than Au or Ad Ronan McNulty, LHCEWWG, 5.04.2011

  7. Where are we most sensitive? HORACE: Born 7TeV. All rapidities. Greatest sensitivity per event at 82 GeV About 2/3 that sensitivity at 91 GeV But much more stats. So measurement on pole appears most sensitive to sin2q far from pole HORACE: Born 7TeV. All rapidities. near pole Ronan McNulty, LHCEWWG, 5.04.2011

  8. Problems for LHC Ronan McNulty, LHCEWWG, 5.04.2011

  9. Going forward increases AFB HORACE: Born 7TeV. 89.2<m<93.2. Ronan McNulty, LHCEWWG, 5.04.2011

  10. Going forward increases sensitivity… HORACE: Born 7TeV. 86.2<m<96.2. Ronan McNulty, LHCEWWG, 5.04.2011

  11. HORACE: Born 7TeV. Stat uncertainty 10fb-1 Stat uncertainty 50fb-1 Ronan McNulty, LHCEWWG, 5.04.2011

  12. 50fb-1 at 14 TeV measures sin2q~0.0001 1fb-1 HORACE: Born 14TeV. 10fb-1 50fb-1 Stat uncertainty 10fb-1 Stat uncertainty 50fb-1 Ronan McNulty, LHCEWWG, 5.04.2011

  13. 50fb-1 at 14 TeV measures sin2q~0.0001 1fb-1 HORACE: Born 14TeV. 10fb-1 50fb-1 Stat uncertainty 10fb-1 • How confident are we: • - of theory? • - of PDF uncertainties? • of detector systematics? Stat uncertainty 50fb-1 Ronan McNulty, LHCEWWG, 5.04.2011

  14. Uncertainty due to PDF Uncertainty from PDF (from one PDF set) about the same as statistical uncertainty. With time, this should improve (~ 50%?) For 3<yZ<4 0.0004 AFB calculated MSTW Eigenvector number Ronan McNulty, LHCEWWG, 5.04.2011

  15. Uncertainty due to PDF HORACE: Born 7TeV. 86.2<m<96.2. Difference between two (old) PDF sets about the same as statistical uncertainty. 0.0004 Ronan McNulty, LHCEWWG, 5.04.2011

  16. Conclusions • Is it worth trying to measure AFB at LHC? • …. Probably. Ronan McNulty, LHCEWWG, 5.04.2011

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